To traverse as many states as possible for large-size circuits, evaluation function is defined which is optimized as it assumes an increased difference in pseudo-primary output value (state) from the past hysteresis. States are searched so as to optimize this evaluation function. Thus, a state transition graph is created. An evaluated value-calculating portion calculates an evaluated value. An evaluated value partial differential coefficient-calculating portion calculates the partial differential coefficient of the evaluated value with respect to the input value. An input-setting portion estimates the direction of search for inputs from this value and searches for states. This state transition graph generator is coupled to the prior art RTP method to generate test patterns.